Hone language at university (6,2)
I believe the answer is:
polish up
'hone' is the definition.
(polishing up is a kind of honing)
'language at university' is the wordplay.
'language' becomes 'polish' (Polish is a language).
'at university' becomes 'up' (slang term meaning at university).
'polish'+'up'='POLISH UP'
(Other definitions for polish up that I've seen before include "Buff" , "Work at (something) in order to improve" .)